Method and apparatus for hot rolling ferrous metal workpieces

ABSTRACT

FERROUS METAL WORKPIECES ARE ROLLED AT AN ELEVATED HOT ROLLING TEMPERATURE IN A HOT MILL USING AN AQUEOUS DISPERSION OF AN OILY LIQUID AS A COOLANT AND LUBRICANT FOR THE WORK ROOLS OF THE ROLLING STANDS. THE AQUEOUS DISPERSION CONTAINS ABOUT 0.0005-0.05% BY WEIGHT OF AN OILY LIQUID HAVING A HIGH FLASH POINT WHICH IS CAPABLE OF ACTING AS A LUBRICANT AT THE ROLLING TEMPERATURES AND PRESSURES. PREFERRED OILY LIQUIDS INCLUDE RAPESEED OIL AND SYNTHETIC RAPESEED OIL THE OILY LIQUID IS INJECTED UNDER HIGH PRESSURE INTO A HIGH-PRESSURE WATER STREAM TO FORM THE DISPERSION AND THE DISPERSION IS SPRAYED ONTO THE WORK ROOLS. FLOW OF OILY LIQUID IS DISCONTINUED BEFORE THE WORKPIEKCE LEAVES THE MILL, FOR THE TAIL END PORTION OF THE HOT WORKPIECE STO REMOVE OIL ON THE ROLLS TO AVOID SLIPPAGE WHEN THE NEXT WORKPIECE ENTERS THE ROLL BITE. FLOW OF OILY LIQUID IS INITIATED ONLY AFTER THE WORKPIECE ENTERS THE ROLL BITE.

Sept. 20, 1971 LYON ETAL 3,605,473

METHOD AND APPARATUS FOR HOT ROLLING FERROUS METAL WORKPIECES Filed larch 21. 1969 V Y 2 Sheets-Shout z I I '3 L- United States Patent US. Cl. 72-201 31 Claims ABSTRACT OF THE DISCLOSURE Ferrous metal workpieces are rolled at an elevated hot rolling temperature in a hot mill using an aqueous dispersion of an oily liquid as a coolant and lubricant for the work rolls of the rolling stands. The aqueous dispersion contains about 0.0005-0.05% by weight ofan oily liquid having a high flash point which is capable of acting as a lubricant at the rolling temperatures and pressures. Preferred oily liquids include rapeseed oil and synthetic rapeseed oil. The oily liquid is injected under high pressure into a high-pressure water stream to form the dispersion and the dispersion is sprayed onto the work rolls. Flow of oily liquid is discontinued before the workpiece leaves the mill, for the tail end portion of the hot workpiece to remove oil on the rolls to avoid slippage when the next workpiece enters the roll bite. Flow of oily liquid is initiated only after the workpiece enters the roll bite.

RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 779,274, filed Nov. 26, 1968 (now abandoned), which is a continuation-in-part of application Ser. No. 760,665, filed Sept. 18, 1968, and now abandoned.

This invention broadly relates to an improved method and apparatus for hot rolling ferrous metal workpieces in a hot mill wherein the workpieces are passed at an elevated hot rolling temperature through a rolling stand having water-cooled work rolls. In some of its more specific variants, the invention further relates to an improved method and apparatus for preparing an aqueous dispersion of an oily liquid and then utilizing the aqueous dispersion as a coolant and lubricant for work rolls during the hot rolling of hot ferrous metal workpieces.

It is known that roll life can be extended markedly in cold mills for cold rolling ferrous metal strip by utilizing an aqueous emulsion of rolling oil as a lubricant. A more uniform cold rolled ferrous metal product is produced with better surface properties and the overall cost of production is lower.

The maximum temperature that is encountered in the cold rolling of ferrous metal strip in a cold strip mill usually is about 400 F. The rolling continuously gencrates heat, and the heat in the driven work rolls and the cold strip may be readily dissipated and controlled by utilizing the aqueous emulsion of rolling oil of the prior art as a lubricant. The aqueous emulsion must con- 3,605,473 Patented Sept. 20, 1971 tain a minimum of 2% by weight of rolling oil to produce a worthwhile improvement, and usually a much higher concentration of oil is required for commercially acceptable results such as up to 20% by weight. Also, an emulsifier must be present to stabilize the aqueous emulsion.

The prior art method of lubricating work rolls in a cold mill is entirely unsatisfactory for use in the hot rolling of ferrous metal workpieces in a hot mill. A number of unique problems are presented by hot mills as the ferrous metal workpieces are usually rolled at temperatures of 1550 F. or above. Application of the oil emulsion which is used in cold mills to the work rolls in hot mills, or to the hot ferrous metal workpieces produces objectionable fuming and smoking, and the rolling oil and its thermal decomposition products deposit on the rolling stands and other equipment in the vicinity. There is also undue slippage between the work rolls and the hot workpieces and cobbles are a problem. Attempts to modify the hot rolling method by applying the rolling oil directly to the backup or work rolls also did not meet with success. In addition to the above mentioned problems, an inversion of the oil and cooling water occurred and awhite foamy substance was formed which was deposited on the equipment.

The present invention overcomes the problems of the prior art and provides for the first time an entirely satisfactory method and apparatus for preparing and utilizing a coolant and lubricant for the work rolls in a hot mill for rolling ferrous metal workpieces. As a result, the average roll life in hot mills and the tonnage rolled per roll are increased markedly, and downtime, the cost of rolls, roll reclaiming, power consumption and related charges are decreased very substantially. Additionally, the hot rolled product is more uniform, it has a much better surface, and the product is of a higher quality in general.

It is an object of the present invention to provide a novel method and apparatus for hot rolling ferrous metal workpieces at elevated temperature in a hot mill wherein an improved coolant for the Work rolls is provided.

It is a further object to provide a novel method and apparatus for preparing the roll coolant of the invention and thereafter utilizing the same as a coolant and lubricant for the work rolls in a hot mill for hot rolling ferrous metal workpieces.

It is still a further object to provide a novel method and apparatus for applying the coolant and lubricant of the invention to the work rolls in a hot mill during the rolling of hot ferrous metal workpieces.

Still other objects and advantages of the invention will be apparent to those skilled in the art upon reference to the following detailed description and accompanying drawings.

-In the drawings, where similar reference characters denote similar elements throughout the several views:

FIG. 1 schematically depicts a hot strip rolling mill embodying principles of the invention;

FIG. 2 is a diagrammatic side elevational view of a rolling stand of the hot strip mill of FIG. 1;

FIG. 3 is a diagrammatic rear elevational view of the rolling stand of FIG. 2; and

FIG. 4 is a view of details of the structure of FIG. 3.

In accordance with the present invention, ferrous metal workpieces are rolled in hot mills including rolling stands having a water-cooled work rolls by an improved method wherein a source is established of an oily liquid to be described more fully hereinafter, a controlled amount of the oily liquid is intimately mixed with water to obtain a dispersion thereof, and then the dispersion is utilized as a coolant for the work rolls during rolling of the hot workpieces.

The oily liquid should be dispersed in the water in an amount of about 0.0005-0.05% by weight. At oily liquid contents less than about 0.0005 by weight, a worthwhile improvement is not obtained, and at oily liquid contents above about 0.05% by weight, there is objectionable slippage between the work rolls and the workpiece. Preferably, the water should contain about (LOUIS-0.03% by weight of the dispersed oily liquid.

The oily liquid should have a high Cleveland open cup flash point such as 225800 F., and preferably about 300700 F. Oily liquids having a Cleveland open cup flash point between about 450 and 650 F. usually produce the best results and are preferred in most instances. The oily liquid should be capable of acting as a lubricant as the rolling pressure, and for best results the oily liquid and/or its thermal decomposition products also should have the ability of continue acting as a lubricant or have at least some lubricating properties as the oil oxidizes on the roll surfaces when in contact with the hot workpiece. Additionally the oily liquid and/or its decomposition products should not form a deposit on the rolling stands and other equipment in the vicinity, and the oily liquid should be capable of being burned off or otherwise removed from the roll surfaces by contacting the same with the hot workpiece.

Specific examples of suitable oils include rapeseed oil and synthetic rapeseed oil. As used herein, the term synthetic rapeseed oil embraces not only rapeseed oil which has been synthesized by other than natural means, but also other artificially produced materials having the prop erties of natural rapeseed oil. Synthetic rapeseed oil has many of the desirable properties of natural rapeseed oil when used in the environment of the present invention, and it may comprise glyceride or vegetable oils as a major constituent. One form of synthetic rapeseed oil is available commercially, e.g. from Quaker Chemical Corporation, Conshohocken, Pa., under the trademark Quakerol HB-l. Synthetic rapeseed oil is characterized by the following typical physical and chemical characteristics:

Property:

Physical appearance Data Free fatty acidity Brown liquid.

as oleic acid by weight maximum. Flash point 460 F. (Cleveland open cup). Fire point 520 F. (Cleveland open cup). Pour point 32 F. Viscosity, S.U.S. 650 at 100 F. and

85 at 210 F. Viscosity index 120. Weight per gallon 7.84 pounds. Ash Less than 0.1% by weight.

Other oily liquids which may be used include those employed heretofore for lubrication of molds in the continuous casting of molten ferrous metal. Lubricants suitable for use in continuous casting are disclosed in an article by W. G. Ritter entitled Lubrication in the Continuous Casting Process appearing in the February 1967 issue of Iron and Steel Engineer, the disclosure of which is incorporated herein by reference. Continuous casting lubricants include vegetable oils in general such as rapeseed oil, linseed oil, cottonseed oil, and cramble oil, animal oils in general including whale oil, and mineral oils of relatively high viscosity such as those supplied to the industry as Continuous Casting Oil No. 2 by the Sun Oil Company and Continuous Casting Oil Lubricant A by the American Oil Company.

Typical data for mineral oil continuous casting lubricants and refined rapeseed oil are as follows:

Data

Mineral oil Refined Property lubricant rapeseed oil Viscosity S.U.S.:

0 107 218 210 F 39 5s Viscosity index 156 Flashpoint, Cleveland open cup, D 290 640 Pour point, F 60 0 Gravity, A.P.l 37. 5 23. 1 Color, ASIM 1 0. 5 Water, weight percent 0. 01 0. 036 Surface tension, dynes/cm.:

11 23. 9 33. 5 to stand 20 minutes) Carbon residue, by weight, percent 0 0. 25 Oxides and ash, by weight, percent 0 0. 003

Slightly cloudy.

The oily liquid may be dispersed in the Water in the above mentioned critical amounts by any convenient method which is effective to produce a dispersion. For instance, the oily liquid may be admixed with the water under turbulent conditions of agitation which produce a finely divided dispersion, and thereafter sufiicient agitation is provided to maintain the small particless of oily liquid dispersed in the water until it is utilized as a coolant and lubricant for the work rolls. One preferred method of forming the dispersion is by injecting the required amount of the oily liquid under high pressure into flowing water under high pressure. Other convenient methods include the use of rotary agitators and other devices designed to produce turbulent conditions of agitation.

It has been further discovered that improved results are obtained when the aqueous dispersion of the oily liquid is substantially free of a detergent or emulsifying aid. The droplets of oily liquid in the dispersion, coat and adhere to the roll surfaces much better in the absence of a detergent or emulsifier, and improved lubrication of the rolls is obtained. A higher percentage of the oily liquid content of the cooling water is also deposited on the roll surface.

Oily liquids having high flash points usually are more easily dispersed in the water after reducing the viscosity by heating to an elevated temperature. In instances where rapeseed oil is the oily liquid, it is usually preferred to preheat the oil to about F., and then mix it with water at the lowest available temperature.

In one preferred variant of the invention, the dispersion is prepared shortly before it is used as a coolant for the work rolls. This is conveniently accomplished by injecting the oily liquid under high pressure into a high pressure Water stream which is flowing immediately upstream of a series of spray nozzles. The high pressure injection of a thin stream of the oily liquid results in intense agitation and the oil is immediately dispersed in the Water in the form of fine droplets. The injection may be effected in a conduit immediately upstream of high pressure sprays and as the water is flowing rapidly therein, the dispersed oil does not have time to settle before it is sprayed onto the work rolls.

The use of high pressure sprays to apply the dispersion to the work rolls is preferred as the dispersed particles of the oily liquid are more intimately contacted with the metallic roll surfaces and are deposited thereon more efficiently. This is especially true when the dispersion is free of a detergent or emulsifying agent.

For best results the dispersion is applied to the rolls of a given rolling stand only after the workpiece has entered the bite of the work rolls, and application is discontinued before the workpiece leaves the bite. This allows the oily liquid to be removed from the roll surfaces by action of the hot workpiece before entry of the next workpiece into the bite and undue slippage and cobbles are prevented.

Preparation of the dispersion by the technique described herein is especially advantageous in instances where it is desired to use the dispersion as a coolant and lubricant during only a portion of the rolling time, and wherein it is desired that water be supplied as a coolant at all other times. In such instances, high pressure cooling water may be supplied to the work rolls on a continuous basis using a header and sprays such as described hereinafter. The dispersion is prepared as it is used by injecting oil into the water flowing to the header over the desired portion of the rolling cycle, using an onoif mechanism for controlling oil flow.

The aqueous dispersion of oily liquid may be utilized as a coolant in a wide variety of hot mills in which ferrous metal workpieces are passed at an elevated hot rolling temperature through rolling stands having work rolls. Specific examples of prior art mills include hot strip mills, hot sheet mills, hot plate mill, hot rod mills, hot bar mills and hot rail mills. The invention is especially useful in continuous hot strip mills, and especially in hot strip mills which produce strip in, e.g., 80 or 96 widths at high strip speeds. The ferrous metal workpieces may be composed of low carbon steel or other prior art steels which may be hot rolled.

It has been discovered that the dispersion containing the small amount of oily liquid acts as a lubricant as well as a coolant as the oily liquid content thereof concentrates on the roll surfaces. The use of the dispersion described herein as a coolant for the work rolls overcomes the problems associated with prior art usage of rolling oils in hot mills. At the same time all of the advantages of the use of a lubricant for the work rolls are obtained, such as markedly increased roll life, a sharply reduced number of work rolls needed for rolling a given tonnage of steel, faster rolling speeds, and uniformity of product, and much less downtime. Unexpectedly, the backup rolls do not pick up scale when using the dispersion as a coolant as is observed when using only water as a coolant. As a result, the backup rolls remain clean and free of scale.

In some instances, it may be desirable to body, blow or partially oxidize semi-drying vegetable oils or drying vegetable oils before they are used in the present invention. This will result in higher flash points and viscosities, and thus semi-drying and drying oils which have relative 1y low initial flash points and viscosities may be improved markedly for the purposes of the invention.

A specific example of operation in accordance with the invention will be presented with the following detailed discussion of the drawings. In the drawings, FIG. 1 schematically illustrates a hot strip rolling mill in which steel slabs are heated to hot rolling temperatures in a furnace 10. The hot slabs are sequentially ejected from the furnace at temperatures of about 2000-2400 F., depending upon the grade of steel and the desired final gage. The slabs are deposited on a roller table including a plurality of rollers 12, and are conveyed by the rollers along the first portion of a pass line 14. Each steel wonkpiece follows pass line 14 throughout its travel through the strip mill.

The heated workpiece is first passed through a series of roughing roll stands (not shown), as is conventional. The workpiece is then passed to a finishing train of four rolling stands 16, 18, and 22. It 'will be appreciated that hot steel strip mills may and usually do include more than four finishing stands. However, the inventive principles involved are applicable whether more or fewer than four rolling stands are employed, and such principles will be understood from a description of a four-stand finishing train. In the drawings, each rolling stand and its associated cooling and lubricating apparatus is identical to the others except as specified hereinafter, so description of one will impart understanding of all to the extent of their identity.

Rolling stand 16 includes upper and lower work rolls 24, 26, which are rotatably carried in a mill housing 28 (FIGS. 2, 3) and have a diameter of about 28". Work rolls 24, 26 are provided backing support by backup rolls 30, 32 respectively, each of which is about 60" in diameter and is rotatably carried by mill housing 28.

A water supply main 34 (FIG. 1) forms a source of water for the roll coolant and lubricating system of each rolling stand. Water in conduit 34 is at a temperature of about F., and is maintained at a pressure of about 200 p.s.i. by a pump 36. A connection 35 including a relief valve 37 is provided to bleed the pump discharge should pressure in conduit 34 become too high. Conduit 34 supplies water to a branch conduit 38 for rolling stand 16, and into corresponding branches for the other roll stands. A valve 39 in conduit 38 controls the flow of water to rolling stand 16. The water is river water, and as such is impure. Hence, as used herein, the term water refers to a substance consisting essentially of water and does not exclude presence-of impurities and/or additives which would not materially affect the cooling and lubricating properties of dispersions in accordance with the invention.

Branch conduit 38 divides into conduits 40, 42 which respectively supply water to oil injection connections 44, 46 in which rapeseed oil is mixed with the water to produce a dispersion of the oil in the water. Conduits 40, 42 conduct the dispersion from the oil injection connections to spray headers 50, 48 (FIGS. 2, 3) respectively. Spray headers 48, 50 respectively include a plurality of nozzles 52, 53 which spray the oil-water dispersion onto upper and lower work rolls 24, *26 respectively.

Oil supplied to the oil injection connections is drawn from an oil reservoir 54 (FIG. 1) in which the oil is maintained at a temperature of about 100 F. A pump 56 forces oil from reservoir '54 through an oil supply conduit 58 at a pressure of about 300 p.s.i. Oil in conduit 58 flows past a connection 60 for a relief valve 62, which opens in the event of unduly high pressure in oil conduit 58 to bleed pump discharge back into reservoir 54. Beyond relief valve connection 60, oil flowing in conduit '58 passes through a flow meter 64, which measures oil consumption.

An on-otf control valve 66 is located in conduit 58 downstream of flow meter 64. Valve 66 controls the flow of oil through conduit 58 by opening or closing the conduit to oil flow. Downstream of control valve 66, oil supply conduit 58 services a branch conduit 68 for rolling stand 16, and similar branch conduit for the other rolling stands. Branch conduit 68 divides into conduits 70, 72 which supply oil to oil injection connections 44, 46 respectively. Oil lines 7 0, 72 respectively include check valves 74, 76 which prevent backflow of flow into the oil system when oil flow is discontinued. Needle valves 78, 80 are respectively inserted in oil lines 70, 72 for closely controlling the rate of fiow of oil through the lines. Each needle valve is located downstream of the associated check valve, and adjacent the respective oil injection connection. The needle valves and oil injection connections are identical, so description of one imparts an understanding of all.

Oil injection connection 46 (FIG. 4) includes a hollow cylindrical member 82- which is welded to water conduit 42. An orifice 84 is formed in the sidewall of the water conduit within the confines of cylindrical member 82, which is internally threaded for connection to oil line 72. The construction forms a continuous oil passageway 86 which intersects at right angles the water passageway 88 defined by the inside walls of conduit 42. Injection of oil under about 300 p.s.i. pressure from passageway 86 into water passageway 88 and into the water flowing therein under about 200 p.s.i. pressure, generates turbulent conditions of agitation in conduit 42in the region of connection 46, intimately mixing oil with the water and causing the oil to be broken into fine droplets which are immediately dispersed in the high-pressure stream of rapidly flowing water. The rapeseed oil droplets are prevented from settling out by turbulence in the portion of conduit 42 which is downstream of connection 46, and by immediate transfer of the dispersion through that portion of conduit 42 and through spray header 48 and spray nozzles 52. Also, the dispersion is prepared as needed. Hence, no detergent or emulsifying aid to stabilize the dispersion is necessary.

It will be appreciated that the oil pump is operative to maintain a higher pressure in oil passageway 86 than prevails in water passageway 88, so that oil can be injected into the flowing water stream. Oil passageway 86 has a cross-sectional area which is appreciably less than that of the water passageway, because of the small amount of oil which is required to produce the cooling and lubricating dispersions of the invention. For example, water conduit 42 and oil line 72 can be of three-inch and one half inch nominal sizes, respectively.

Needle valve 80 can be of any type of conventional design suitable for closely controlling the rate of oil flow through oil line 72. Needle valve 80 includes a valve body 90, a stem 92 and a hand wheel 94. Rotation of hand wheel 94 moves stem 92 axially in valve body 90 to increase or decrease the rate of flow of oil through orifice 96 and thus through oil line 72. The quantity of oil that is injected is carefully controlled and is based on the flow rate of high-pressure water to the spray headers to provide about 0.0005-0.05% of oil by weight. When water I fiow rate is altered for any reason, the needle valve setting is adjusted to alter the oil flow rate to maintain the dispersion at the desired oil percentage.

Rolling stand 22 (FIG. 1), which is the last stand in terms of rolling sequence, differs from the other stands in that it includes a load detecting cell 98 which is operative 1y connected to oil control valve 66. The load cell can be of any suitable type of conventional design, and detects entry of a workpiece head end into the work roll bite of rolling stand 22. When a workpiece enters the rolling stand, the cell operates through connection 100 to open valve 66 and initiate oil flow through oil supply line 58 and hence into the oil lines to the oil injection connections of each of the four rolling stands. Oil is thus simultaneously supplied to all the stands. By this arrangement in which oil flow to all stands is initiated on a single command from the last stand, all the work rolls take a bite on the workpiece before lubricant flow is started. This is advantageous because it avoids slippage which is tended to be caused when rolls attempt to bite a workpiece with lubricant on the rolls and/or the workpiece.

Along pass line 14, ahead of rolling stand 16 is located a heat radiation sensor 102, which can be of any suitable type of conventional design, e.g., a radiation pyrometer. When the tail end of the hot workpiece in the rolling train leaves heat sensor 102, which because of the spacing between the heat sensor and rolling stand 16 is indicative of the approach of the workpiece tail end to rolling stand 16, heat sensor 102 operates through a connection 104 to close oil control valve 66 to stop oil flow through oil supply line 58 and thus terminate flow of oil to each of the oil injection connections in the rolling train. However, water continues to be applied to the work rolls from water supply conduit 34 to cool the rolls, because the tail end portion of the hot workpiece is still in the mill. Oil flow is discontinued while a portion of the workpiece is still in the mill to allow time for oil on the work rolls to be evaporated, burned oif or otherwise removed by action of the hot workpiece, so that the work rolls will be suificiently free of lubricant to take a bite on the next workpiece without slipping. The time required for removal of oil from the work rolls by contact with the workpiece depends not only on the number of revolutions of the work rolls, but also on the number of revolutions of the backup rolls because the work rolls pick up oil from the backup rolls. Accordingly, heat sensor 102 is spaced from first rolling stand '16 a distance equal to at least 1-2 times the circumference of the backup rolls to allow time for sufficient area of the hot workpiece to contact the work rolls to effect oil removal from the first rolling stand 16. It will be appreciated that the oil is also removed from the rolls of the other stands by the tail end portion of the workpiece. Connections 100, 104, through which sensors 98, 102 respectively operate, can be of any suitable type of conventional design, e.g., pneumatic, electromechanical, or other type of control.

A summary of operation of the hot strip mill will be initiated on the assumption that oil control valve 66 is closed so that no oil is flowing to the oil injection connections. Valves 39 are open, so water is supplied to the work rolls from the spray headers. A hot slab is passed from furnace 10, roughed and then passed sequentially into rolling stands 16, 18, 20 and 22. On entry of the workpiece head end into the roll bite of stand 22, load cell 98 opens valve 66 so that oil flows through the oil supply lines to the oil injection connections to initiate transverse injection of oil into the water passageways of each stand to produce an oil-water dispersion which is supplied to all the work rolls through the respective spray headers. When the workpiece tail end leaves heat sensor 102, the sensor closes valve 66 to terminate flow of oil to the injection connections so that again only cooling Water is applied to the work rolls. The workpiece, reduced to e.g. about 0.100 gage, passes out of the mill at a temperature of at least about 1550 F. with the oil on the work rolls being removed during the last revolutions of the rolls so that the rolls of each stand will bite the next workpiece without slipping. Water control valves 39 can be closed when no workpiece is in the mill, and can if desired be opened in sequence as a workpiece successively enters the respective stands.

While operating as described above, there was no undue slippage between the work rolls and the workpiece and cobbles were not a problem. Also, the oil or its decomposition products did not form a deposit on the mill stands and other equipment, nor was there excessive fuming and smoking. The surface of the rolled product was greatly improved. Downtime was decreased markedly, roll life was greatly extended, and the rate of production increased substantially. These results markedly contrast with those of a similar operation in which the rapeseed oil was applied separately by spraying onto the rolls instead of in a dispersion with the cooling water. The oil and water formed a white foamy substance which deposited on the mill housing. There was some slippage of the workpiece in the mill, and excessive white smoke and fumes were given off from the hot ferrous metal workpiece. Thus, application of the cooling water and rapeseed oil separately does not produce acceptable results. Likewise, in another otherwise-similar operation in which an aqueous oil emulsion containing an excess of 2% by weight of oil and an emulsifier was used instead of the dispersion of the invention, the same problems occurred as with separate application of oil.

The hot rolling mill can include more or fewer than four rolling stands. Further, a cooling and lubricating system according to the invention can be provided only on selected stands of a multiple-stand mill and the selected stands can be separated from one another by stands not serviced by the system. It can be desirable in individual lnstances to supply dispersions with differing oil percentages to different rolling stands in the same rolling train, and/or to upper and lower spray headers at the same rolling stand, depending upon the oil percentages found to optimize results at a given stand. For operating flexibility it can be desirable in some instances to provide separate sections of a rolling train with its own separate coolant and lubricant system, eg to divide a seven-stand rolling train into a first section of four stands and a second section of three stands, each with its own cooling and lubricating system. Also, while the workpieces herein described are heated to hot rolling temperatures in furnace 10, hot workpieces can be provided by other means, e.g., a continuous caster. Accordingly, the foregoing detailed description has been provided for purposes of illustration only. For definition of the scope of the invention, reference will be made to the appended claims.

We claim:

1. In a method of hot rolling ferrous metal workpieces in a hot mill wherein the workpieces are passed at an elevated hot rolling temperature of at least about 1550 F. through a rolling stand having work rolls, the improvement which comprises establishing a source of oily liquid which is capable of acting as a lubricant at rolling pressures and which has a high flash point, intimately mixing water and the oily liquid to obtain a dispersion of oily liquid in the water, and utilizing the oily liquid and water dispersion as a coolant for the work rolls during rolling of the hot workpiece, the oily liquid being dispersed in the water in an amount between about 0.0005 and about 0.05% by weight of the water.

2. The method of claim 1 wherein the oily liquid has a Cleveland open cup flash point of at least about 225 F. and not greater than about 800 F.

3. The method of claim 1 wherein the oily liquid comprises rapeseed oil.

4. The method of claim 1 wherein the oily liquid comprises synthetic rapeseed oil.

5. The method of claim 1 wherein the water containing the oily liquid dispersed therein is applied to the rolls by means of a high pressure spray whereby dispersed particles of the oily liquid are intimately contacted with the roll surfaces and deposited thereon.

6. The method of claim 1 wherein the mixing of the oily liquid with the water is under turbulent conditions of agitation whereby a finely divided dispersion of the oily liquid in the water is formed.

7. The method of claim 1 wherein the dispersion of the oily liquid in the water is free of a detergent.

8. The method of claim 7 wherein the oily liquid when mixed with the water is at an elevated temperature at which the viscosity of the oily liquid is reduced to thereby aid in forming the dispersion in the absence of a de tergent.

9. The method of claim 1 wherein the dispersion of oily liquid in the water is formed in the mixing step by injecting the oily liquid into the water.

10. The method of claim 1 wherein the oily liquid is dispersed in the water in an amount between about 0.0015% and about 0.03% by weight of the water.

11. The method of claim 1 wherein the dispersion of a the oily liquid in the water is applied to the rolls of the rolling stand after the workpiece has entered the bite of the rolls, and the application of the dispersion is discontinued before the workpiece leaves th bite of the rolls to thereby allow oily liquid to be removed from the roll surfaces before entry of the next workpiece.

12. The method of claim 11 wherein the oily liquid has a Cleveland open cup flash point between about 300 F. and about 700 F.

13. The method of claim 12 wherein the water containing the oily liquid dispersed therein is applied to the rolls by means of a high pressure spray whereby dispersed particles of the oily liquid are intimately contacted with the roll surfaces and deposited thereon.

14. The method of claim 13 wherein the oily liquid is mixed with the cooling water in the mixing step under turbulent conditions of agitation in the absence of a detergent whereby a dispersion of the oily liquid in the water is formed.

15. The method of claim 14 wherein the oily liquid has a Cleveland open cup flash point between about 450 F. and about 650 F. and the oily liquid is dispersed in the water in an amount between about 0.0015 and about 0.03% by weight of the water.

10 16. The method of claim 15 wherein the oily liquid comprises rapeseed oil.

17. The method of claim 15 wherein the oily liquid comprises synthetic rapeseed oil.

18. Apparatus for hot rolling ferrous metal workpieces, comprising means for providing hot ferrous metal workpieces at a temperature of at least about 1550 F., at least one rolling stand including work rolls, means for conveying hot workpieces to the rolling stand along a pass line, means defining a source of oily liquid, means defining a source of water, at least one dispersing means communicating with the source of water and with the source of oily liquid for mixing oily liquid with water under turbulent conditions of agitation to produce a dispersion of oily liquid in water, and fluid transfer means for transferring dispersion to each rolling stand to cool and lubricate the work rolls. 19. The apparatus of claim 18, each dispersing means including means defining a water passageway communicating with the source of water, and means defining an oily liquid passageway communicating with the source of oily liquid and intersecting the water passageway for injecting oily liquid into the water passageway. 20. The apparatus of claim 19, including sensing means for sensing approach of a workpiece tail end to a rolling stand, and control means responsive to the sensing means for stopping fiow through each oily liquid passageway upon approach of the workpiece tail end to the rolling stand. 21. The apparatus of claim 20, including first and second rolling stands, the first rolling stand being the rolling stand associated with the sensing means, the pass line extending in a direction from the first rolling stand to the second rolling stand, detecting means associated with the second rolling stand for detecting entry of the workpiece into the work roll bite of the second rolling stand, and the control means being responsive to the detecting means for initiating flow through each oily liquid passageway upon entry of the workpiece into the work roll bite of the second rolling stand. 22. The apparatus of claim 20, the sensing means including a heat detector spaced from the rolling stand a distance to permit the workpiece tail end portion to effect removal of oily liquid from the work rolls. 23. The apparatus of claim 19, including means for maintaining a high pressure in the water passageway, and means for maintaining in the oily liquid passageway a pressure which is higher than the pressure in the water passageway. 24. The apparatus of claim 19, including needle valve means for controlling rate of flow through each oily liquid passageway. 25. The apparatus of claim 19, the oily liquid passageway having a cross-sectional area which is substantially less than the cross-sectional area of the water passageway. 26. The apparatus of claim 18, the fluid transfer means including means for spraying dispersion onto the work rolls. 27. The apparatus of claim 18, each fluid transfer means including spray means for spraying dispersion onto a single work roll, each dispersing means communicating with a single spray means. 28. The apparatus of claim 18,

1 1 each dispersing means being located adjacent a rolling stand to prevent oily liquid from settling out of the dispersion before being transferred to cool and lubricate the work rolls.

29. The method of claim 1, wherein the water and oily liquid are mixed at a location adjacent the rolling stand to prevent oily liquid from settling out of the dispersion before utilization as a coolant for the work rolls.

30. The apparatus of claim 18, including sensing means for sensing approach of a workpiece tail end to a rolling stand, and

control means responsive to the sensing means for interrupting communication between the source of oily liquid and each dispersing means upon approach of the workpiece tail end to the rolling stand.

31. The method of cairn 1 wherein application of the dispersion at the rolling stand is discontinued before the workpiece leaves the bite of the rolls to thereby allow oily liquid to be removed from the roll surfaces before entry of the next workpiece.

References Cited UNITED STATES PATENTS 2,303,142 11/1942 Spangler 72-42X 2,310,563 2/1943 Wilke 3d et a1 72236X 2,933,956 4/1960 Snow 7213 3,192,752 7/1965 Dowd et al. 72-45 3,208,253 9/1965 Roberts 72201X 3,429,815 2/1969 Drake -1" 252-49.5

FOREIGN PATENTS 241,307 5/1960 Australia.

OTHER REFERENCES Lubrication in the Continuous Casting Process, by

' Wayne G. Ritter, Iron and Steel Engineer, February 1967,

MILTON S. MEHR, Primary Examiner US. Cl. X.R.

Z32 3? UNITED STATES PATENT OFFICE -CER'IIFICATIE OF CORRECTION Patent No. 3,605,473 Dated September 20, 1971 Lockwood Lyon and William H. Rees I: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

line 1, dele'te theword "a"-.

.column 3,

Column 3, line ,22; "as" should read at Column 3', line .24, "of" should read to Column 3, the beginning of, the table should read;

: 'PrOEe'rty r T Data A Physical appearance Brown liquid.

Free fatty acidity 5% by weight maximum.

as Oleic' acid v V Column ,3, line 72, "cramble" should read crambe Q Column 4, 'in the table after li'ne l9 and before line 20 "36" should read 36.2

Column 4, line 30, "'part ioles s should read pari z icles Column 5, line 2 2, "mill" should read.-- mills Column 11, line 16, "daim". shoul d read claim L s1gnea d a1ad this 25th dayof March 1972. i

Attest; I

EDwARD MQFLETCHER', JR; 1 y a ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

